Papilledema

Papilledema is swelling of the optic disc caused by raised intracranial pressure. Because the pressure is transmitted along the optic nerve sheath, the swelling is characteristically bilateral, and its recognition on examination of the back of the eye is an important clue to elevated pressure within the skull.

Definition

Papilledema is optic disc edema produced by elevated intracranial pressure transmitted through the subarachnoid space surrounding the optic nerve, and is by convention restricted to disc swelling of this cause.

Scope

This entry covers papilledema as the optic-disc manifestation of raised intracranial pressure: its mechanism, why it is typically bilateral, how it differs from other causes of disc swelling, and its central role in the pseudotumor cerebri / idiopathic intracranial hypertension syndrome. The term papilledema is reserved for disc swelling due to raised intracranial pressure, distinguishing it from optic disc edema of other causes.

Core questions

• How is papilledema from raised intracranial pressure distinguished from optic disc swelling of other causes?
• What systemic and neurological conditions does bilateral disc swelling point toward?
• How does papilledema fit into the diagnostic framework for idiopathic intracranial hypertension?

Key concepts

• Raised intracranial pressure
• Optic nerve sheath
• Bilateral optic disc swelling
• Idiopathic intracranial hypertension (pseudotumor cerebri)
• Axoplasmic flow stasis
• Visual field loss from chronic disc swelling

Mechanisms

Elevated intracranial pressure is transmitted through the cerebrospinal fluid in the subarachnoid space that surrounds the optic nerve, raising pressure within the optic nerve sheath. This impedes axoplasmic transport within optic nerve fibers at the disc, causing the nerve-fiber layer to swell and the optic disc to appear elevated, typically in both eyes. Because the mechanism is pressure transmitted along a shared pathway, papilledema is generally bilateral, and persistent swelling can lead to progressive damage of nerve fibers and visual-field loss.

Clinical relevance

Papilledema is clinically important as a visible sign of raised intracranial pressure, which can arise from mass lesions, venous outflow problems, or idiopathic intracranial hypertension, so its recognition connects an ocular finding to the need for neurological evaluation. The revised diagnostic criteria for the pseudotumor cerebri syndrome (Friedman, 2013) formalize how papilledema is incorporated into that diagnosis. This entry is descriptive reference material and not a basis for individual diagnostic or treatment decisions.

Epidemiology

Idiopathic intracranial hypertension, a common cause of papilledema in the absence of a mass lesion, occurs predominantly in younger women, and its incidence rises with obesity, paralleling trends in body weight. The Idiopathic Intracranial Hypertension Treatment Trial (Wall, 2014) studied this population.

Evidence & guidelines

The revised diagnostic criteria for the pseudotumor cerebri syndrome (Friedman, 2013) provide the contemporary framework for diagnosing idiopathic intracranial hypertension, in which papilledema is central. The Idiopathic Intracranial Hypertension Treatment Trial (Wall, 2014) is the principal randomized evidence on managing visual outcomes in this syndrome. Walsh and Hoyt's Clinical Neuro-Ophthalmology (Miller & Newman, 2005) gives the broader textbook account of disc swelling.

History

The link between optic disc swelling and raised intracranial pressure has been recognized since the development of ophthalmoscopy in the nineteenth century. The syndrome of raised pressure without a mass lesion, long called pseudotumor cerebri and later idiopathic intracranial hypertension, was progressively defined through the twentieth century, culminating in revised consensus diagnostic criteria (Friedman, 2013) and dedicated treatment trials (Wall, 2014).

Debates

How should papilledema be distinguished from pseudopapilledema and other disc swelling?

Apparent disc elevation from buried optic disc drusen and other congenital anomalies (pseudopapilledema) can mimic true papilledema, and reliably separating swelling caused by raised intracranial pressure from other causes of disc edema remains a practical diagnostic challenge.

Seminal works

• friedman-2013
• wall-2014

Frequently asked questions

Why is papilledema usually present in both eyes?

Because the swelling is driven by raised pressure inside the skull that is transmitted equally along the sheaths of both optic nerves, papilledema characteristically affects both eyes; one-sided disc swelling is more likely to have a different, local cause.

Is all optic disc swelling called papilledema?

No. By convention the term papilledema is reserved for disc swelling caused by raised intracranial pressure; disc edema from other causes, such as inflammation or ischemia of the optic nerve, is described with different terms.